<!DOCTYPE html>
<html lang="zh-Hans">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>CSS3 - 根据宽度百分比绘制正方形</title>
    <style>
        .square-box {
            margin: 200px auto;
            width: 20%;
            padding-bottom: 20%;
            background: red;
            border-radius: 50%;
            position: relative;
        }
        .text {
            font-size: 2em;
            color: #fff;
            letter-spacing: 2px;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
        }
    </style>
</head>
<body>
    <div class="square-box">
       <span class="text">CHINA</span>
    </div>
</body>
</html>